排序方式: 共有71条查询结果,搜索用时 15 毫秒
1.
1. As for some other spring‐feeding moths, adult flight of Epirrita autumnata (Lepidoptera: Geometridae) occurs in late autumn. Late‐season flight is a result of a prolonged pupal period. Potential evolutionary explanations for this phenological pattern are evaluated. 2. In a laboratory rearing, there was a weak correlation between pupation date and the time of adult emergence. A substantial genetic difference in pupal period was found between two geographic populations. Adaptive evolution of eclosion time can thus be expected. 3. Metabolic costs of a prolonged pupal period were found to be moderate but still of some ecological significance. Pupal mortality is likely to form the main cost of the prolonged pupal period. 4. Mortality rates of adults, exposed in the field, showed a declining temporal trend from late summer to normal eclosion time in autumn. Lower predation pressure on adults may constitute the decisive selective advantage of late‐season flight. It is suggested that ants, not birds, were the main predators responsible for the temporal trend. 5. Egg mortality was estimated to be low; it is thus unlikely that the late adult period is selected for to reduce the time during which eggs are exposed to predators. 6. In a laboratory experiment, oviposition success was maximal at the time of actual flight peak of E. autumnata, however penalties resulting from sub‐optimal timing of oviposition remained limited. 相似文献
2.
ATR and ATM kinases are central to the checkpoint activation in response to DNA damage and replication stress. However, the nature of the signal, which initially activates these kinases in response to UV damage, is unclear. Here, we have shown that DDB2 and XPC, two early UV damage recognition factors, are required for the damage-specific ATR and ATM recruitment and phosphorylation. ATR and ATM physically interacted with XPC and promptly localized to the UV damage sites. ATR and ATM recruitment and their phosphorylation were negatively affected in cells defective in DDB2 or XPC functions. Consequently, the phosphorylation of ATR and ATM substrates, Chk1, Chk2, H2AX, and BRCA1 was significantly reduced or abrogated in mutant cells. Furthermore, UV exposure of cells defective in DDB2 or XPC resulted in a marked decrease in BRCA1 and Rad51 recruitment to the damage site. Conversely, ATR- and ATM-deficiency failed to affect the recruitment of DDB2 and XPC to the damage site, and therefore did not influence the NER efficiency. These findings demonstrate a novel function of DDB2 and XPC in maintaining a vital cross-talk with checkpoint proteins, and thereby coordinating subsequent repair and checkpoint activation. 相似文献
3.
Nicolas Gobron Cezary Waszczak Matthieu Simon Sophie Hiard Stéphane Boivin Delphine Charif Alo?se Ducamp Estelle Wenes Fran?oise Budar 《PloS one》2013,8(4)
Gynodioecy, the coexistence of hermaphrodites and females (i.e. male-sterile plants) in natural plant populations, most often results from polymorphism at genetic loci involved in a particular interaction between the nuclear and cytoplasmic genetic compartments (cytonuclear epistasis): cytoplasmic male sterility (CMS). Although CMS clearly contributes to the coevolution of involved nuclear loci and cytoplasmic genomes in gynodioecious species, the occurrence of CMS genetic factors in the absence of sexual polymorphism (cryptic CMS) is not easily detected and rarely taken in consideration. We found cryptic CMS in the model plant Arabidopsis thaliana after crossing distantly related accessions, Sha and Mr-0. Male sterility resulted from an interaction between the Sha cytoplasm and two Mr-0 genomic regions located on chromosome 1 and chromosome 3. Additional accessions with either nuclear sterility maintainers or sterilizing cytoplasms were identified from crosses with either Sha or Mr-0. By comparing two very closely related cytoplasms with different male-sterility inducing abilities, we identified a novel mitochondrial ORF, named orf117Sha, that is most likely the sterilizing factor of the Sha cytoplasm. The presence of orf117Sha was investigated in worldwide natural accessions. It was found mainly associated with a single chlorotype in accessions belonging to a clade predominantly originating from Central Asia. More than one-third of accessions from this clade carried orf117Sha, indicating that the sterilizing-inducing cytoplasm had spread in this lineage. We also report the coexistence of the sterilizing cytoplasm with a non-sterilizing cytoplasm at a small, local scale in a natural population; in addition a correlation between cytotype and nuclear haplotype was detected in this population. Our results suggest that this CMS system induced sexual polymorphism in A. thaliana populations, at the time when the species was mainly outcrossing. 相似文献
4.
Cremona Fabien Laas Alo Hanson Paul C. Sepp Margot Nõges Peeter Nõges Tiina 《Ecosystems》2019,22(4):805-817
Ecosystems - We assessed the allochthonous organic carbon (OC) budgets for thirteen hemiboreal lakes using a simple equilibrium model coupled with a Bayesian framework for estimating parameter... 相似文献
5.
Freitak D Ots I Vanatoa A Hõrak P 《Proceedings. Biological sciences / The Royal Society》2003,270(Z2):S220-S222
Parasite-driven coevolution has led hosts to develop a complicated and potentially costly defence machinery, consisting mainly of the immune system. Despite the evidence for the trade-offs between immune function and life-history traits, it is still obscure how the costs of using and maintaining the immune function are paid. We tested whether immune challenge is energetically costly for white cabbage butterfly (Pieris brassicae L.) diapausing pupa. Individuals challenged with nylon implant raised their standard metabolic rate nearly 8% compared to the controls. Hence, costs of activation of immune system in insect pupa can be expressed in energetic currency. 相似文献
6.
7.
This paper describes sand flies similar to Nyssomyia intermedia (Lutz & Neiva) with variations in the number of spines at the gonostyle and tests the hypothesis whether these specimens belong or not to N. intermedia species. Using Principal Component Analysis and Neighbour Joining, the measurements of 15 structures of the phlebotomine with variations in number of spines were compared with measurements of 30 sand flies of N. intermedia species. Both analyses didn't cluster the specimens with variation in spines number in one group and provided evidence to the hypothesis that those sand flies belong to N. intermedia. 相似文献
8.
9.
Enno Merivee Alo Vanatoa Anne Luik Märt Rahi Väino Sammelselg Angela Ploomi 《Physiological Entomology》2003,28(2):88-96
Abstract. In single-sensillum extracellular electrophysiological recordings, terminal campaniform sensilla at the tip of antennae of the ground beetle Pterostichus aethiops (Pz., 1797) show action potentials of three sensory cells, A-, B- and C-cells, distinguished by differences in their spike amplitudes. Only the A-cell, with the largest spike amplitude, is highly sensitive to temperature fluctuations, showing remarkable changes in its firing rate induced by changes in temperature of 0.1 °C. The firing rate of A-cells at 23 °C varies from 15–52 Hz among different beetles. Mean impulse frequency of A-cells is found to be a function of steady temperature, the firing rate decreasing with temperature increase. A-cells respond to a rapid temperature drop with a strong phasic-tonic reaction; larger decreases in temperature evoke higher peak frequency values. Maximum peak frequencies, varying from 380–630 Hz in different beetles, are induced by temperature decreases of 3–10 °C, whereas temperature rise strongly inhibits impulse activity of the A-cell. The first manifestation of rapid warming in the nerve impulse sequence is a very long interspike period, followed by diminished activity. Both the length of the long interspike period and the rate of following impulse activity are functions of temperature change; hence, A-cells respond to temperature changes as typical cold receptors, similar to coeloconic and short hair-like sensilla in other insects. 相似文献
10.